Untitled Page

MORE Programs Poster Presentation

December 1, 2006

Title: Expression of Adenylyl Cyclase IX in the Rat Ovary

Authors: Jerlisa Arizala, Dr. Philip S. LaPolt

The production of estradiol (E2) by the ovary is vital to the development and maintenance of the female reproductive system.  E2 synthesis is increased by follicle-stimulating hormone (FSH), which acts on G protein-coupled receptors in the ovary, increasing activity of a membrane-associated enzyme, adenylyl cyclase (AC).  Activated AC converts adenosine triphosphate (ATP) into adenosine 3’,5’ cyclic monophosphate (cyclic AMP), which activates signaling mechanisms that induce the expression of enzymes required for E2 synthesis.  There are several isoforms of AC, and surprisingly little information is available regarding the AC isoforms expressed in the ovary.  Preliminary analysis of AC isoform mRNA levels suggests that ACIX may be a predominant isoform in the ovary.  The goal of this project is to examine the cell-specific regulation of ACIX protein levels in the rat ovary during follicle development, ovulation, and luteinization.  Immunoblot analysis was used to detect the presence and regulated levels of ACIX protein in ovarian protein homogenates.  Immunocytochemistry was used to determine the cellular localization and regulation of ACIX protein in immature, hormone-treated  rat ovary at different time points (E0, E52, H8, and H72).  Ovarian protein homogenates were subjected to SDS-PAGE gel fractionation and electrophoretically transferred to PVDF membranes.  A predominant immunoreactive signal of about 161 kDa in rat ovarian tissue, corresponding to the reported size of ACIX protein, was observed during immunoblot analyses of ACIX protein levels.  Subsequent immunocytochemical analysis revealed cell-specific expression and hormonal regulation of ACIX in the oocyte and immediately adjacent surrounding granulosa cells of developing follicles in eCG and hCG-treated immature rat ovary.  However, the majority of granulosa cells do not express ACIX.   These findings indicate that ACIX is expressed in the ovary primarily in oocytes, suggesting a role of this enzyme in regulating cAMP-dependent inhibition of oocyte maturation.